One verse

Srimad Bhagavatam 11.16.12

11.16.12

हिरण्यगर्भो वेदानां मन्त्राणां प्रणवस्‍त्रिवृत् । अक्षराणामकारोऽस्मि पदानिच्छन्दसामहम् ॥ १२ ॥

hiraṇyagarbho vedānāṁ mantrāṇāṁ praṇavas tri-vṛt akṣarāṇām a-kāro ’smi padāni cchandasām aham

hiraṇya-garbhaḥ
Lord Brahmā
vedānām
of the Vedas
mantrāṇām
of mantras
praṇavaḥ
the oṁkāra
tri-vṛt
consisting of three letters
akṣarāṇām
of letters
a-kāraḥ
the first letter, a
asmi
I am
padāni
the three-line Gāyatrī mantra
chandasām
among sacred meters
aham
I am

Among the Vedas I am their original teacher, Lord Brahmā, and of all mantras I am the three-lettered oṁkāra. Among letters I am the first letter, “a,” and among sacred meters I am the Gāyatrī mantra.